On the plus-side for you guys I've greatly improved the HDR Demo sample that I wrote. Look out for that in a future SDK. [wink].
In an addendum to the Oren-Nayar entry... courtesy of a PM from rollo I've realised that there the Sin()Tan() map is actually going to be essential for a ps_2_0 version. From preliminary research, the pure mathematical expansion of that term will vastly exceed the limits of a ps_2_0 profile [lol]
Ward Reflection Model
The Ward reflection model (published in the SIGGRAPH 1992 proceedings) is one of the better models for simulating metalic surfaces. It varies the specular component based on the "direction" of the surface... thus being able to mimmick brushed metallic surfaces (amongst other things)...
And, as usual, a pretty Visio diagram: